The present invention relates to a switch, and relates in particular to a switch wherein a click spring is located on the upper face of a fixed contact formed on a circuit board, and wherein the upper face of the circuit board is shielded by an insulating cover film.
A related-art switch of this type, i.e., a membrane switch, will now be described while referring to FIG. 4. Such a membrane switch 1 comprises: a circuit board 2; switch portions S, each of which includes a center fixed contact 3 and a circumferential fixed contact 4, both of which are arranged on the circuit board 2, and a hemispherical metal click spring 5 arranged over and on the fixed contacts 3 and 4; a spacer 6 formed on the circuit board 2; and an insulating cover film 7, which is bonded, using an adhesive M, to the upper faces of the click springs 5 and the spacer 6.
When the membrane switch 1 is incorporated in an electronic apparatus, such as a portable telephone or a keyboard, multiple switch portions S are sequentially arranged on the upper face of the circuit board 2, and the cover film 7 is bonded, using the adhesive M, to click springs 5 and the upper face of the spacer 6, which is mounted on the circuit board 2.
When one of the switch portions S is depressed directly or through pressure applied using a key top (not shown), the curved, raised portion of the click spring 5 is depressed and inverted, and the center of the lower face of the click spring 5 is brought into contact with the center fixed contact 3. The circumferential fixed contact 4 and the center fixed point 3 are thus rendered conductive by the click spring 5, and the switch portion S is turned on.
In this example, the adhesive M is also used to bond the spacer 6 to the circuit board 2. However, each switch portion S may be constituted by simply mounting a spacer 6 on the upper face of the circuit board 2 without using the adhesive M.
In the configuration wherein the adhesive is used to bond the spacer to the circuit board, when repair of the switch portions is required, the cover film to which the click springs and the spacer are bonded can not easily be removed from the circuit board because the spacer is securely attached thereto by the adhesive. Repairing the circuit board, therefore, is also impossible.
In the configuration wherein the spacer is merely mounted on the circuit board, repairs are possible; however, since no adhesive is used to seal a switch portion, foreign substances, such as dust or fluids, tend to enter a switch and to present an obstacle to electric contact, thereby contributing to a conductivity failure.
It is therefore an object of the present invention to provide a switch wherein the sealing of a switch portion can be accomplished by adhering a spacer to the upper face of a circuit board, and a cover film, to which a click spring and the spacer are bonded, can be easily removed from the circuit board to facilitate the repair of the switch portion.
In order to achieve the above object, according to the present invention, there is provided a switch, comprising:
a circuit board;
a first conductive member and a second conductive member, disposed on a first face of the circuit board;
a click spring, disposed on the first conductive member and deformed so as to establish an electrical contact between the first conductive member and the second conductive member, when a depressing force is applied thereto;
an insulating film, disposed above the click spring;
a spacer, interposed between the insulating film and the circuit board such that a first face thereof opposes to a first face of the insulating film and a second face thereof opposes to the first face of the circuit board; and
a first adhesive layer, interposed between the first face of the circuit board and the second face of the spacer; the first adhesive layer having a viscosity such an extent that the spacer and the circuit board are detached from each other without damage.
In this configuration, the spacer can be easily removed from the circuit board. Therefore, not only the maintenance of the switch is extremely easy, but also the entry of foreign substances that can act as obstacles to the conduct of electricity can be prevented because the first adhesive layer serves to shield a switch portion (constituted by the conductive members and the click spring) of the switch from the outside, so that conductive failures will not occur.
Preferably, the first adhesive layer is comprised of at least one of acryl and silicon.
Preferably, the viscosity of the first adhesive layer is adjusted in accordance with a thickness thereof.
In this configuration, since the thickness can be arbitrarily adjusted in accordance with the materials employed for the circuit board and the spacer, the spacer can be stably adhered to the circuit board, and can be easily detached from the circuit board.
Preferably, the first adhesive layer is a screen-printed layer.
In this configuration, formation of the first adhesive layer can be performed accurately. And further, because this process can be automated, the amount of labor it requires can be reduced.
Preferably, the switch further comprises a second adhesive layer, provided on a second face of the insulating film, on which an external member is mounted, the second adhesive layer having a viscosity such an extent that the external member and the insulating cover are detached from each other without damage.
In this configuration, the second adhesive layer can be used to attach electronic parts, such as key tops, to the insulating film. Subsequently, adhering the electronic parts to or removing them from the cover film can be performed quickly and easily. Therefore, if a key top, for example, is broken, it can be easily exchanged as part of the normal maintenance for the keyboard.
Here, it is preferable that the second adhesive layer is comprised of at least one of acryl and silicon.
Further, it is preferable that the viscosity of the second adhesive layer is adjusted in accordance with a thickness thereof.
Still further, it is preferable that the second adhesive layer is a screen-printed layer.
According to the present invention, there is also provided a switch, comprising:
a circuit board;
a first conductive member and a second conductive member, disposed on a first face of the circuit board;
a click spring, disposed on the first conductive member and deformed so as to establish an electrical contact between the first conductive member and the second conductive member, when a depressing force is applied thereto;
an insulating film, disposed above the click spring;
a first adhesive layer, provided on a first face of the insulating film, on which an external member is mounted, the first adhesive layer having a viscosity such an extent that the external member and the insulating cover are detached from each other without damage.
Preferably, the first adhesive layer is comprised of at least one of acryl and silicon.
Preferably, the viscosity of the first adhesive layer is adjusted in accordance with a thickness thereof.
Preferably, the first adhesive layer is a screen-printed layer.
Preferably, the switch further comprises:
a spacer, interposed between the insulating film and the circuit board such that a first face thereof opposes to a second face of the insulating film and a second face thereof opposes to the first face of the circuit board; and
a second adhesive layer, interposed between the first face of the circuit board and the second face of the spacer, the second adhesive layer having a viscosity such an extent that the spacer and the circuit board are detached from each other without damage.
Here, it is preferable that the second adhesive layer is comprised of at least one of acryl and silicon.
Further, it is preferable that the viscosity of the second adhesive layer is adjusted in accordance with a thickness thereof.
Still further, it is preferable that the second adhesive layer is a screen-printed layer.